Abstract

In this letter, we describe a technique for determining the Andreev reflection probability of electrons impinging on a semiconductor–superconductor interface. A two-dimensional electron gas(2DEG) in an InGaAs/InP heterostructure is linked to a niobiumsuperconductor. A point contact in the 2DEG emits ballisticelectrons and detects the reflected carriers. The vast majority of the detected carriers are retroreflected holes because of our specific sample setup. We have found an Andreev reflection probability of up to 20%. The experimental results are compared with the predictions of two theoretical models.